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The National Research Council (NRC) released its long-awaited update on the Comprehensive Nuclear Test-Ban Treaty (CTBT) last Friday. Given the renown of the scientists and former officials who authored the report, it is likely to have an important impact on the longstanding debate over whether the United States should ratify the CTBT.

The report itself concludes that over the past decade the United States has significantly improved the technical capabilities needed both to maintain a reliable nuclear weapon stockpile without nuclear explosion testing and to detect clandestine testing by others. By thus addressing two of the major concerns raised when the treaty was rejected by the Senate in 1999, the report clearly strengthens the position of those who favor ratification now.

The CTBT prohibits states from carrying out "any nuclear weapon test explosion or any other nuclear explosion." It also lays out in great detail the means for monitoring compliance, including the establishment of a worldwide network of more than 300 detection stations and provisions for on-site inspection. Interestingly, the treaty does not specifically define "nuclear explosion." The United States and the other major nuclear powers have consistently held that the CTBT is a "zero yield" treaty. In other words, it bans weapon tests that produce a self-sustaining, fission chain reaction; but, it does not preclude weapon experiments that do not. Such experiments—and the subsequent analysis performed on increasingly powerful computers—have played a critical role in assessing the health of the nuclear weapons stockpile since the United States unilaterally stopped testing in 1992.